The search for life on other planets has been based on what we already know. But what if extraterrestrial life does not look like any beings we’re used to on Earth? It may even be unrecognizable to the scientists searching for it. In this essay, Sarah Scoles meets Sarah Stewart Johnson, who has been looking for “aliens” from a different perspective.

Even when scientists do discover biology unfamiliar to them, they tend to relate it to something familiar. For instance, when Antonie van Leeuwenhoek saw single-celled organisms through his microscope’s compound lens in the 17th century, he dubbed them “animalcules,” or little animals, which they are not.